This study aims to characterize the unique globular tail domain of one of the most well-studied unconventional myosins, myosin V (M5). Severe defects in this myosin are lethal in species ranging from yeast to man, and null mutations result in neurological, immunological, and pigmentation abnormalities in mammals. The function of M5 is unknown; however, current genetic and biochemical data demonstrates that this myosin binds organelles and may be required for some form of organelle transport. This study aims to characterize the binding of M5 to these organelles, and to isolate and characterize vesicle proteins that interact with myosin V using affinity chromatography, protein microsequencing, yeast two-hybrid screening, and molecular cloning techniques. Furthermore, the proposed studies aim to elucidate the function of these interactions through in vitro analysis of how binding effects motor function, and through phenotypic analysis and biochemical characterization of murine alleles deficient in these binding interactions. Although the short term aims of this study are simple to characterize the binding proteins that interact with the tail of M5, over the long term these studies are not only likely to contribute to our understanding of unconventional motor proteins, but may also facilitate a greater understanding of the basic processes that re essential to cell function.